src/gromacs/random/tests/threefry.cpp

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  35 /*! \internal \file
  36  * \brief Tests for the ThreeFry random engine
  37  *
  38  * \author Erik Lindahl <erik.lindahl@gmail.com>
  39  * \ingroup module_random
  40  */
  41 #include "gmxpre.h"
  42
  43 #include "gromacs/random/threefry.h"
  44
  45 #include <gtest/gtest.h>
  46
  47 #include "gromacs/utility/exceptions.h"
  48
  49 #include "testutils/refdata.h"
  50 #include "testutils/testasserts.h"
  51
  52 namespace gmx
  53 {
  54
  55 namespace
  56 {
  57
  58 class ThreeFry2x64Test : public ::testing::TestWithParam<std::vector<gmx_uint64_t> >
  59 {
  60 };
  61
  62 TEST_P(ThreeFry2x64Test, Default)
  63 {
  64     gmx::test::TestReferenceData       data;
  65     gmx::test::TestReferenceChecker    checker(data.rootChecker());
  66     const std::vector<gmx_uint64_t>    input = GetParam();
  67     std::vector<gmx_uint64_t>          result;
  68
  69     gmx::ThreeFry2x64<0>               rng(input[2], input[3]);
  70     rng.restart(input[0], input[1]);
  71
  72     result.push_back(rng());
  73     result.push_back(rng());
  74
  75     checker.checkSequence(result.begin(), result.end(), "ThreeFry2x64");
  76 }
  77
  78 TEST_P(ThreeFry2x64Test, Fast)
  79 {
  80     gmx::test::TestReferenceData       data;
  81     gmx::test::TestReferenceChecker    checker(data.rootChecker());
  82     const std::vector<gmx_uint64_t>    input = GetParam();
  83     std::vector<gmx_uint64_t>          result;
  84
  85     gmx::ThreeFry2x64Fast<0>           rng(input[2], input[3]);
  86     rng.restart(input[0], input[1]);
  87
  88     result.push_back(rng());
  89     result.push_back(rng());
  90
  91     checker.checkSequence(result.begin(), result.end(), "ThreeFry2x64Fast");
  92 }
  93
  94 TEST_P(ThreeFry2x64Test, Using40Rounds)
  95 {
  96     gmx::test::TestReferenceData       data;
  97     gmx::test::TestReferenceChecker    checker(data.rootChecker());
  98     const std::vector<gmx_uint64_t>    input = GetParam();
  99     std::vector<gmx_uint64_t>          result;
 100
 101     gmx::ThreeFry2x64General<40, 0>    rng(input[2], input[3]);
 102     rng.restart(input[0], input[1]);
 103
 104     result.push_back(rng());
 105     result.push_back(rng());
 106
 107     checker.checkSequence(result.begin(), result.end(), "ThreeFry2x64Using40Rounds");
 108 }
 109
 110
 111 /*! \brief Constant array of integers with all bits zeroed.
 112  *
 113  *  Reference key and counter input data for known answers test.
 114  *  The 2x64 flavors of ThreeFry64 will use the first four values, while
 115  *  the 4x64 version uses all eight.
 116  */
 117 const std::vector<gmx_uint64_t> bitsZero {{
 118                                               0, 0, 0, 0
 119                                           }};
 120
 121
 122 /*! \brief Constant array of integers with all bits set to one.
 123  *
 124  *  Reference key and counter input data for known answers test.
 125  *  The 2x64 flavors of ThreeFry64 will use the first four values, while
 126  *  the 4x64 version uses all eight.
 127  */
 128 const std::vector<gmx_uint64_t> bitsOne {{
 129                                              0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL,
 130                                              0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL
 131                                          }};
 132
 133 /*! \brief Constant array of integers with bitpattern from Pi.
 134  *
 135  *  Reference key and counter input data for known answers test.
 136  *  The 2x64 flavors of ThreeFry64 will use the first four values, while
 137  *  the 4x64 version uses all eight.
 138  */
 139 const std::vector<gmx_uint64_t> bitsPi {{
 140                                             0x243f6a8885a308d3ULL, 0x13198a2e03707344ULL,
 141                                             0xa4093822299f31d0ULL, 0x082efa98ec4e6c89ULL
 142                                         }};
 143
 144 // Test the known ansers for the ThreeFry random function when the argument
 145 // is (1) all zero, (2) all ones, (3) the bits of pi, for a bunch of different flavors of ThreeFry.
 146 INSTANTIATE_TEST_CASE_P(KnownAnswersTest, ThreeFry2x64Test,
 147                             ::testing::Values(bitsZero, bitsOne, bitsPi));
 148
 149
 150 // ThreeFry2x64 tests
 151 TEST_F(ThreeFry2x64Test, Logical)
 152 {
 153     gmx::ThreeFry2x64<10> rngA(123456, gmx::RandomDomain::Other);
 154     gmx::ThreeFry2x64<10> rngB(123456, gmx::RandomDomain::Other);
 155     gmx::ThreeFry2x64<10> rngC(123456, gmx::RandomDomain::Other);
 156
 157     rngB();              // draw just once first, so block is the same, but index has changed
 158     EXPECT_NE(rngA, rngB);
 159     rngC(); rngC();      // two draws: next block, but index is the same
 160     EXPECT_NE(rngA, rngC);
 161     rngA();
 162     EXPECT_EQ(rngA, rngB);
 163     rngA();
 164     EXPECT_EQ(rngA, rngC);
 165 }
 166
 167 TEST_F(ThreeFry2x64Test, InternalCounterSequence)
 168 {
 169     gmx::test::TestReferenceData     data;
 170     gmx::test::TestReferenceChecker  checker(data.rootChecker());
 171
 172     // 66 bits of internal counter means the first four increments (giving 2*4=8 results)
 173     // correspond to incrementing word 0, and then we should carry over to word 1.
 174     gmx::ThreeFry2x64<66>        rngA(123456, gmx::RandomDomain::Other);
 175     std::vector<gmx_uint64_t>    result;
 176
 177     for (int i = 0; i < 16; i++)
 178     {
 179         result.push_back(rngA());
 180     }
 181     checker.checkSequence(result.begin(), result.end(), "ThreeFry2x64InternalCounterSequence");
 182
 183     // Make sure nothing goes wrong with the internal counter sequence when we use a full 64-bit word
 184     gmx::ThreeFry2x64<64>        rngB(123456, gmx::RandomDomain::Other);
 185     for (int i = 0; i < 16; i++)
 186     {
 187         rngB();
 188     }
 189
 190     // Use every single bit for the internal counter
 191     gmx::ThreeFry2x64<128>        rngC(123456, gmx::RandomDomain::Other);
 192     for (int i = 0; i < 16; i++)
 193     {
 194         rngC();
 195     }
 196 }
 197
 198 TEST_F(ThreeFry2x64Test, Reseed)
 199 {
 200     gmx::ThreeFry2x64<10> rngA(123456, gmx::RandomDomain::Other);
 201     gmx::ThreeFry2x64<10> rngB;
 202
 203     EXPECT_NE(rngA, rngB);
 204     rngB.seed(123456, gmx::RandomDomain::Other);
 205     EXPECT_EQ(rngA, rngB);
 206     rngB();                                      // internal counter increments
 207     rngB.seed(123456, gmx::RandomDomain::Other); // reseeding should reset random stream too
 208     EXPECT_EQ(rngA, rngB);
 209 }
 210
 211 TEST_F(ThreeFry2x64Test, Discard)
 212 {
 213     gmx::ThreeFry2x64<10> rngA(123456, gmx::RandomDomain::Other);
 214     gmx::ThreeFry2x64<10> rngB(123456, gmx::RandomDomain::Other);
 215
 216     for (int i = 0; i < 9; i++)
 217     {
 218         rngA();
 219     }
 220     rngB.discard(9);
 221     EXPECT_EQ(rngA, rngB);
 222 }
 223
 224
 225 TEST_F(ThreeFry2x64Test, InvalidCounter)
 226 {
 227     gmx::ThreeFry2x64<10> rngA(123456, gmx::RandomDomain::Other);
 228
 229     // Highest 10 bits of counter reserved for the internal counter.
 230     EXPECT_THROW_GMX(rngA.restart(0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF), gmx::InternalError);
 231 }
 232
 233 TEST_F(ThreeFry2x64Test, ExhaustInternalCounter)
 234 {
 235     gmx::ThreeFry2x64<2> rngA(123456, gmx::RandomDomain::Other);
 236
 237     // 2 bits for internal counter and 2 64-results per counter means 8 results are fine
 238     for (int i = 0; i < 8; i++)
 239     {
 240         rngA();
 241     }
 242     // ... but the 9th time we have exhausted the internal counter space.
 243     EXPECT_THROW_GMX(rngA(), gmx::InternalError);
 244 }
 245
 246 }      // namespace anonymous
 247
 248 }      // namespace gmx